Transcript GI_System
DIGESTION – the process of changing
foods into simpler soluble forms to be
absorbed by body
ALIMENTARY CANAL
Digestive tract or gastrointestinal tract
(GI Tract).
A 30 ft. tube from mouth to anus.
Functions of the Digestive
System
Physical breakdown
Chemical digestion of food
Absorb nutrients
Eliminate waste products
Lining of the Digestive System
PERITONEUM – double-layered serous
membrane that lines the abdominal cavity
Parietal layer lines the abd. cavity
Visceral layer lines the organs of the
abd. cavity
Peritoneum has 2 “parts”
Mesentery attaches to the posterior wall
of abd.
Greater omentum attaches to anterior
wall of abd.
Peritonitis inflammation/infection of the
peritoneum
4 Layers of the GI Tract
1. Mucosa layer secrets a “slimy mucus”
This mucus coats the food AND
helps protect the organs from the
corrosive enzymes in the GI tract
2. Sub mucosa layer lies under mucosa
layer and contains blood vessels and
nerves
3.
4.
Circular muscle layer bands of muscles
that are circular
Longitudinal muscle layer bands of
muscles that run length wise on the GI
tract
The muscle layer help perform
“peristalsis”
Wave like motion that pushes food
through the GI tract
Structure of Organs of Digestion
MOUTH
Food enters digestive system through
mouth
“buccal cavity”
Inside of mouth covered with mucous
membrane
Roof of mouth is HARD PALATE (bone)
and soft palate
UVULA – flap that hangs off soft palate –
prevents food from going up the nose when
you swallow
TONGUE
Helps
in chewing and swallowing
Made of skeletal muscle
> 9000 taste buds (papillae) on
the surface
Also sensitive to heat, cold and
pressure
SALIVARY GLANDS
Three pairs of glands
PAROTID – largest salivary glands
Secrete saliva (about 3 qts. per day)
Salvia is made up of:
1. mucus
to coat the food
2. ptyalin (amylase) starts chemical
breakdown of food
Amylase breaks down carbohydrates or
“starches”
TEETH
GINGIVA – gums
MASTICATION – chewing
Adult mouth has 32 teeth
Teeth are covered with enamel- hardest
substance in the body
Inside the tooth is pulp- contains nerves and
blood vessels
As we chew and mix saliva with our food we
create a “bolus” a soft, ball of food pliable
ESOPHAGUS
Connects pharynx an
stomach
Muscular tube, 10” long
“epiglottis” allows passage of food
into the esophagus
CARDIAC SPHINCTER – circular
muscular valve
controls passage of food into
stomach AND prevents food from
re-entering the esophagus
STOMACH
Upper part of
abdominal cavity
Divided into 3 parts:
1. Fundus upper part
2. Greater curvature
3. Pyloric lower part
SPHINCTER – circular
muscle, valve
PYLORIC
Controls
passage of food into the
small intestines AND prevents
food from coming back into the
stomach
When
the stomach is not distended
with food, it “folds” in on itself,
These folds are called
“Rugae”
The stomach has millions of “gastric
glands” which secrete gastric
juices or enzymes to help digest
food
As
food is chemically digested it
turns into a semi-liquid mixture:
“Chyme”
Chyme
enters the small intestines
SMALL INTESTINE
DUODENUM – first segment of small
intestines, 12” long
Very important because this is where
the common bile duct, liver and
pancreas dump their digestive
enzymes!!!
JEJUNUM – next section, 8 ft. long
ILEUM – final portion, 10-12 feet long
Don’t Jump In!!!
Small
intestines prepare the chyme for
absorption
There are tiny projections from the wall of
the small intestines that increase the
absorption area called:
“villi”
Villi are filled with blood vessels and
absorb the nutrients
Villi
of the Ileum
Undigested parts of
chyme go to the
LARGE INTESTINES
via the ileocecal valve
The small areas below
the ileocecal valve are
the
Cecum and appendix
Cecum and Appendix
They have no known function
Empty slowly and can fill with
bacteria causing
appendicitis
LARGE INTESTINE
also called the colon
Approx 2” in
diameter, has 3
parts:
Ascending colon
Transverse colon
Descending colon
The
last part of the descending colon
curves back into the abd. and forms
an “S” called the
Sigmoid colon
The last 7-8 inches of the colon is
called the rectum
External opening is the anus
Hemorrhoids enlarged rectal veins
Accessory Organs of
Digestion
They don’t come in contact
with the food
1. PANCREAS
Located behind stomach
Exocrine function –
secretes digestive enzymes
into duodenum
Endocrine function secretes
Insulin
LIVER
Largest organ in the
body
Located upper right
quadrant
Main function is to
produce bile
about 800-1000 ccs
of bile per day
The liver has other functions:
store glucose in the form of GLYCOGEN
Detoxify alcohol, drugs and other
harmful substances
Manufacture blood proteins
(fibrinogen and prothrombin)
Liver is connected to
gallbladder and small
intestine by ducts
If the “common bile
duct” becomes
blocked, bile backs up in
the liver and a person
may become
“Jaundiced”
yellow tint to the skin
because the liver can’t
metabolize all the bile
GALL BLADDER
Small green organ, inferior surface of the
liver
Stores and concentrates bile until
needed by the body
When fatty foods digested, bile released
by gallbladder
DIGESTION
In the mouth…
Teeth: begin mechanical breakdown
of the food
Saliva: mucus softens and coats
the food to make it easier to
swallow
PTYALIN in saliva converts starches
into simple sugar
This creates a BOLUS
soft, pliable ball, it slides down
esophagus
Swallowing
begins as a voluntary action,
but as the bolus hits the esophagus, the
process becomes involuntary
In the esophagus:
Peristalsis begins here and the food
continues to be coated with mucus
In the stomach…
gastric (digestive) juices are released
About 2-3 quarts per day
stomach walls churn and mix the
digestive juices and food to create the
chyme
takes
2-4 hours for stomach to empty
Enzymes released by the stomach:
1. protease
2. pepsin
both of these breakdown
proteins (remember p
and p)
3. Hydrochloric Acid (HCL acid) kills the
bacteria in our food
small amount of chyme enters duodenum
at a time - controlled by pyloric
sphincter
In the small intestine…
addition of enzymes from pancreas and
bile from liver/gallbladder
digestion
occurs
is completed and absorption
Enzymes from the Small Intestines
1. Maltase
2. Lactase
3. Sucrase these all break down
glucose
4. lipase
breaks down fats
5. peptidases break down proteins
Enzymes from the Liver/Gall Bladder
1. Bile breaks down fats
Enzymes
from the Pancreas
1. protease breaks down proteins
2. amylase breaks down carbs/starches
3. lipase breaks down fats
4. enzymes to neutralize acidic chyme
Absorption by the villi
can only occur when the end products
of digestion are in these forms:
1. Carbohydrates are converted to glucose
2. Proteins are converted to amino acids
3. Fats are converted to fatty acids and
glycerol
Portal Circulation
How does the liver work as a filter???
“portal veins” picks up the blood
from the villi
blood is transported to the liver
blood is filtered
dumped back into systemic circulation
The
In
the large intestine…
regulation of H2O balance by absorbing
large quantities of H2O back into
bloodstream
If we absorb to much H2O of the waste
material, what do we get?
Constipation
If we absorb to little H2O out of the waste
material, what do we get?
diarrhea
We
have bacteria in our intestines
What is the most common type?
E. coli
It is harmless to us and helps decompose
the undigested food/waste material
It also helps make Vit. K
Why do we need Vit. K?
coagulation
When
this decomposition occurs,
Flatulence or gas is produced
We pass about 1-3 pints /day
The gas of sulfur and methane
give feces it’s odor
Feces undigested semi-solid waste
Feces is stored in the rectum
Feces
is stored in the rectum
When the rectum becomes full,
The defecation reflex is triggered
Defecation
is an involuntary action that
we learn to control
HEARTBURN Acid reflux
burning sensation in throat/chest
Rx – avoid chocolate, coffee,
fried or fatty foods, stop smoking
GERD: gastroesophageal reflux disease
heartburn more than 2-3 times per
week
HIATAL HERNIA stomach protrudes above
the diaphragm through the esophagus
PYLORIC STENOSIS
Narrowing of pyloric sphincter, found in
infants
S/S – projectile vomiting
Rx – surgery to stretch pyloric sphincter
CHOLECYSTITIS
Inflammation of gallbladder
CHOLELITHIASIS Gall stones
Small ones may pass
on their own
Large ones can block the bile
duct causes pain (back, shoulders)
N/V after eating
CHOLECYSTECTOMY surgically
removed of gallbladder
LAPAROSCOPIC
CHOLECYSTECTOMY
Small abdominal incisions (though
belly button area)
allow insertion of surgical instruments
and small video camera
Surgeon performs procedure by
watching monitor and manipulating
instruments
Stomach muscles are not cut, healing
is quicker, less risk of infection
Laproscopic
Surgery
GASTRITIS – acute or chronic
inflammation of the stomach lining
GASTROENTERITIS
Inflammation of mucous membrane
lining of stomach and intestine
S/S – diarrhea and vomiting for 24-36
hours
Complication = dehydration, may
need IV fluids
ULCER
Sore or lesion that forms in the mucosal lining of
the stomach/intestines
Cause – H. pylori (bacteria) is primary cause
Lifestyle factors that contribute: cigarette
smoking, alcohol, stress, certain drugs
S/S – burning pain in abdomen
Antibiotics , antacids
H.
Pylori
COLITIS
(IRRITABLE BOWEL
SYNDROME)
Large intestine inflamed
Cause – unknown, stress
seems to make it worse
– episodes of constipation or
diarrhea
S/S
APPENDICITIS
When appendix becomes inflamed
If it ruptures, bacteria from appendix
can spread to peritoneal cavity
causing PERITONITIS
Treatment appendectomy
HEPATITIS A (Infectious hepatitis)
Spread through contaminated food or H2O
HEPATITIS B (Serum Hepatitis)
Caused by virus found in blood
Transmitted by blood transfusion or being
stuck with contaminated needles (drug addicts)
Health care workers at risk and should be
vaccinated
CIRRHOSIS
Chronic,
progressive disease of liver
Normal tissue replaced by fibrous
connective tissue
75% caused by excessive alcohol
consumption
JAUNDICE – yellow color when bile
pigment gets in bloodstream
COLON CANCER
Early detection critical HEMOCCULT –
stool slide specimen to look for hidden
blood
COLONOSCOPY
after age 50
Rx – colon resection
COLOSTOMY – opening in abdomen,
healthy bowel brought to skin after cancer
removed, pouch worn to collect waste
Cancer of
the
Ascending
colon
CONSTIPATION
When
defecation delayed or
feces become dry and hard
Rx – diet with cereals, fruits,
vegetables, (roughage) or fiber,
drinking plenty of fluids, exercise,
Vomiting
allows stomach to empty
harmful or irritating contents
Hyperemesis
Hyperemesis
excessive vomiting
and diarrhea can lead to
dehydration, may need IV fluids